1. Field of the Invention
The invention is in the field of semiconductor device processing and the devices made thereby. In particular, it relates to providing external electrical contact to compound semiconductors.
2. Decription of the Prior Art
Many multilayer processes for the production of ohmic contact to compound semiconductors are known in the literature. For example, U.S. Pat. No. 3,890.699, issued June 24, 1975 teaches the use of successive layers of gold, silver, and germanium and the subsequent melting of the three layers to produce ohmic contact to N-type gallium arsenide. U.S. Pat. No. 3,850,688, issued Nov. 26, 1974, teaches the deposition of a combination layer of gold and a Group II metallic element over a gold layer to produce ohmic contact to a p-type Group III-V compound semiconductor. Other workers have used epitaxially deposited transition layers (e.g. U.S. Pat. No. 3,914,785, issued Oct. 21, 1975). The literature, however, recognizes the difficulty of contacting aluminum containing compound semiconductors (see, for example, Solid State Electronics, 18 (1975)541 at 549) and suggests the use of a relatively expensive epitaxial deposition process.